Since the light transmission factor of a liquid crystal varies with the voltage applied to the liquid crystal, it is theoretically possible to obtain a desired gradation (gray scale level) by varying the voltage applied across a liquid crystal cell.
However, the change in the light transmission factor of a liquid crystal is large relative to the change in voltage applied to the liquid crystal. Therefore, displays using voltage changes to obtain gray scale require high precision electronic circuits to obtain multiple gradations by adjusting the voltage applied to the liquid crystal.
A liquid crystal display device is disclosed in Published Unexamined Japanese Patent Application (PUPA) No. 58-220185. In that display, one display unit 100 comprises four pixels 101, 102, 104, and 108. These pixels have area ratios of 1:2:4:8, resulting in a 16-gradation (gray scale level) display by the combination of the selection and non-selection of one or more of the four pixels.
However, each display unit 100 of the device described in PUPA No. 58-220185 requires a pixel 108 (see FIG. 7) having an area eight times that of the pixel 101 (the smallest area). Therefore, the ability to reduce the area of a display unit is limited, thus reducing its utility in large area liquid crystal display devices with high resolution.